Top PDF Green Envelop Impact on Reducing Air Temperature and Enhancing Outdoor Thermal Comfort in Arid Climates

Green Envelop Impact on Reducing Air Temperature and Enhancing Outdoor Thermal Comfort in Arid Climates

Green Envelop Impact on Reducing Air Temperature and Enhancing Outdoor Thermal Comfort in Arid Climates

d PhD Candidate, Architectural Engineering Department, Cairo University, Egypt. Received 24 March 2019; Accepted 18 May 2019 Abstract Today Urban Cities faces energy and environmental challenges due to increased population, higher urbanization. The building sector has a big responsibility as it acquires high consumption rates in global energy and environmental scenarios. It is thought that the built environment in Egypt is responsible for 26% of the total overall national energy consumption, 62% of the total electricity consumption and around 70% of resultant CO2 emissions. The increased use of electrical appliances causes Urban Heat Island effect (UHI), which affect major urban centres. Adding green elements to any urban area is proved to be an effective strategy with numerous benefits to enhance the city's ecosystem, also mitigate the urban heat island measures. In this research Green roofs/walls can regulate outdoor air temperature by 10°C and improve outdoor thermal comfort by 2 Predicted Mean Value (PMV) values. The modelling of green strategy models can take into consideration design developments in areas with hot and dry climatic zones. The properties of green walls can directly affect the results of thermal comfort as leafs absorbs, reflects and transmits solar radiation, and increases the evapotranspiration.
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The influence of bioclimatic urban redevelopment on outdoor thermal comfort.

The influence of bioclimatic urban redevelopment on outdoor thermal comfort.

a building due to increased reflectance of solar radiation to building envelope, while the impact on heating demand is negligible. 2.2 Urban green Vegetation affects outdoor thermal comfort not only because of the different properties values (solar reflectance, infrared emissivity, heat capacity etc.) compared to other materials of the built environment, but also due to evapotranspiration procedure. Water loss (water vapor) increases air humidity which leads to an increase of latent cooling (Dimoudi & Nikolopoulou, 2003). Additionally, geometric characteristics of plants (height, tree crown width, leafage shape and density, etc.) determine shading in the urban environment and have a great influence on surface temperatures. For hot climates, shading is the basic factor that prevents the development of very high temperatures, because overheating is mainly caused by storage of heat to sun exposed surfaces (Ali Toudert, 2005). It has been observed that in an urban park the air temperature could be 3- 4°C lower than the surrounding urban area for the noon hours of a summer day (Bernatzky, 1982). Shashua-Bar & Hoffman (2000) have also investigated the cooling effect of shading in small urban green spaces, courtyards and streets in subtropical climate and detected an air temperature difference of 1°C compared to spaces exposed to solar radiation. This difference could reach 3°C for the hottest hours of the day. Regarding energy savings due to urban green, many studies indicate that the cooling effect of shading on building envelopes could conduce to the reduction of cooling demand (Akbari et al., 1997; McPherson et al., 1997; Donovan & Butry, 2009).
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Outdoor thermal comfort by different heat mitigation strategies   a review

Outdoor thermal comfort by different heat mitigation strategies a review

This paper reviewed the impact of different heat mitigation strategies on the pedestrians’ thermal comfort in the context of urban and microclimate. It should be noted that the magnitude of UHI varies in different climates. Consequently, in each climate, a specific heat mitigation strategy is needed. Most of the previous studies have investigated the changes of meteorological variables (such as air temperature deviations) by heat mitigation strategies. Among different heat mitigation strategies, vegetation and high albedo (reflective) surfaces as solutions for improving outdoor thermal comfort in urban spaces were investigated in this paper. Vegetation was studied in the forms of parks, street trees, green roofs and green walls. High albedo materials were then studied while they are used on the roofs (as white roofs) and on the ground surfaces. Through several examples in different countries and climates, it was shown that urban surfaces play an important role on the thermal comfort of pedestrians. Vegetation and high albedo surfaces showed appreciable reduction of air temperatures within urban open spaces. However, mean radiant temperature affects human thermal comfort more than the other
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Enhancement of Outdoor Thermal Comfort through Adoption of Environmental Design Strategies

Enhancement of Outdoor Thermal Comfort through Adoption of Environmental Design Strategies

One of the very few studies on the urban street microclimate which focuses on radiation fluxes confirms the advantage of shading towards a reduction of the radiant heat gained from a human body when compared to a person standing in a fully exposed location [6].Trees as shading elements are very important to urban design. One important impact of street trees on citizens is the reduction of thermal stress during hot meteorological background conditions [7]. There are a few studies on the effect of planting trees on improvement of urban areas especially streets according to thermal comfort. While green cover is one of the most important solutions for creating appropriate micro–climate in harsh climates, especially in hot & dry climates and increase in their seeding is one of the best option to higher the pedestrian comfort level. Street trees will be most effective in providing “true” shade. Trees should be located to maximize shade for pedestrians, such as along walkways and sidewalks. Tree can improve the ambient air temperature by up to 15 % [2]. Studies show that individual trees in high distances will have a little impact on comfort and cooling. Therefore, it has been recommended that it is more effective for urban sites to use several smaller groups of trees [5].
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Effect of Urbanization and Industrialization Processes on Outdoor Thermal Human Comfort in Egypt

Effect of Urbanization and Industrialization Processes on Outdoor Thermal Human Comfort in Egypt

Detailed studies on the effect of urbanization and indus- trialization on human comfort in Greater Cairo region, Egypt have been performed in this study. Four different districts in Greater Cairo region have been selected, namely Bahtim to represent rural area, Cairo Airport to represent suburban area, Abbasiya to represent typi- cal urban area and Helwan to represent industrial area. The data of surface dry, wet bulb temperatures and wind speed for two different periods have been used. The first period (1967-1976 and 1947-1956 for the rural and re- main three districts respectively) represents the old non-urbanized period while the second period (1990-2009 for all districts) represents the recent urban- ized period. Discomfort indices for the two periods have been calculated using Robaa's formula 4. The study re- vealed that urbanization and industrialization processes have resulted in the modification of local city climate. This modification involves the alteration of the local air temperature, humidity and wind speed which in turn cause human climate change. It could be concluded that the urbanization and industrialization processes at any locality cause increase of human serious hot uncomfort- able feeling which in turn leads to more hindering for the human activities while the rural conditions leads to op- timum weather comfort for further and more human ac- tivities.
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Sculpting the "Aesthetics of Air" for Improved Thermal Comfort

Sculpting the "Aesthetics of Air" for Improved Thermal Comfort

Simulations were conducted using the Integrated Environmental Solutions (IES) Virtual Environment software (2014 version). It includes various simulation tools – thermal stimulations, solar shading analysis, day lighting analysis, life cycle analysis, etc. – to assess a building’s environmental performance and inform design. The software provides a dynamic thermal simulation engine called Apache to simulate occupant thermal comfort based on various model inputs such as annual hourly weather data, building geometry and construction, glazing ratios, façade openings, shading, and internal loads. Model inputs used throughout the bulk air flow analyses are further explained in chapter 8. PMV was among the various outputs that Apache produces making it ideal for bulk air flow modeling taking into account the six major factors of thermal comfort.
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Effect of the Shadings Pattern and Greenery Strategies on the Outdoor Thermal Comfort

Effect of the Shadings Pattern and Greenery Strategies on the Outdoor Thermal Comfort

Fig. 1. Location of Iraq and the neighbouring countries . Regarding the investigation study conducted in Iran (Tehran city) on the strategies to reduce the impact of Urban Heat Island on the human health [2], the results showed that the amount of vegetation placed on a building and its position (roofs, walls or both) is a more dominant factor than the orientation of the urban canyon. The canyon geometry with green roofs and walls that had a low thermal impact could play a more important role than the street orientation. Also, the study revealed that the heat sensation zones “hot” and “warm” are not achieved when urban roofs and walls are covered with vegetation, leading to more pleasant and comfort environments for the city residents. An investigation study was conducted of the warm core of Urban Heat Island in the highland zone of Muscat, Oman [3]. The valley is surrounded by mountains formed of dark colored rocks that can absorb the short wave radiation and contribute to the existence of the warmth in the core of the urban area. The study emphasized the importance of the nature of rural baseline when assessing the urban effect on an urban area climate. A study was conducted in Bahrain City [4] to analyze the impact of the urbanization on the thermal behaviour of newly built environments. The results revealed that the recent process of the urbanization leads to an increase in the urban temperature by 2-5 ℃. The increase in temperature is enhanced by the urban activity such as on- going construction processes, shrinkage of green areas and the sea reclamation. Several studies indicate how the green effects have a crucial role in the process of sustainable cooling of the urban planning and in saving energy and
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Evaluation of Thermal Comfort of a Green Building: A Case Study

Evaluation of Thermal Comfort of a Green Building: A Case Study

ABSTRACT: Thermal comfort is a condition of mind that expresses satisfaction with the thermal environment and the same depends on wind velocity, relative humidity, surface temperature, activity level, clothing level etc. This work discusses the evaluation of thermal comfort of a green building during the post monsoon season (October 2016 to December 2016) with respect to the parameters namely temperature, wind velocity, relative humidity and intensity of light. It was found that the surface temperature is more for the rooms located on the south eastern side compared to that of rooms located on the northern side. Average outside relative humidity differs from the indoor humidity by 7%. This is mainly due to the design and orientation of the building. The application of double wall had considerable effect on the wall temperature. From the study it is concluded that the orientation, design and material selection are the key factors which determines the thermal comfort of the building under study.
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Wind characteristics and outdoor thermal comfort assessment in East Malaysia

Wind characteristics and outdoor thermal comfort assessment in East Malaysia

During southwest monsoon season, wind velocity is below 8m/s. Meanwhile, for northeast monsoon season, the wind velocity is in the range of 5 to 10 m/s. Generally, wind velocity is light and inconsistent during inter-monsoons seasons. Annually, Malaysia experiences monthly average relative humidity between 70% to 90%. Additionally, the country has around 6 hours of solar radiation per day on average (MetMalaysia, 2015). This study was aimed at enhancing our understanding of outdoor thermal environment in two different cities in East Malaysia, namely Kuching (i.e. Northwestern part of the Borneo island) and Kota Kinabalu (i.e. West coast of Sabah), as shown in Figure 1 and outlined in Table 1. The wind characteristics and outdoor thermal comfort levels were examined using weather data that correspond with the hot and humid tropical climate of Malaysia from two principal weather stations in Kuching and Kota Kinabalu.
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The impact of increasing urban surface albedo on outdoor summer thermal comfort within a university campus

The impact of increasing urban surface albedo on outdoor summer thermal comfort within a university campus

contributing to rising sea levels, and this makes coastal cities vulnerable. The oldest weather station in the Netherlands is located in De Bilt. This weather data has been recorded since 1901. According to the historical data, the average air temperature has increased 1.4 °C between 1951 and 2013. This increase is twice the global average (KNMI 2015b). The Royal Netherlands Meteorological Institute (KNMI), as the Dutch national weather service has produced four climate scenarios based on IPCC fifth report (IPCC 2013) for 2050 and 2085. Based on these scenarios, air temperature increase for December, January and February (winter) is larger than March, April and May (spring). The temperature changes in the scenarios are briefly described in Table 1. Based on these future scenarios, urban spaces must be designed in a way to mitigate the impact of global warming on citizens` health. A practical way to make urban spaces ready for warmer futures is to adjust the albedo of surfaces. In the following section, the importance of high-albedo materials is explained.
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Solar Radiation Estimation from Rainfall and Temperature Data in Arid and Semi-arid Climates of Iran

Solar Radiation Estimation from Rainfall and Temperature Data in Arid and Semi-arid Climates of Iran

of determination over 0.65 and an index of agreement of 0.889. In case of Esfehan station, none of the models performed well and there was no significant difference observed among them, that might be justified by systematic error or some unknown local climatic conditions which must be further serutinized. In general, the models using temperature only did a better job in Kerman, Zanjan and Hamedan. In mashhad station, the model using rainfall data only (Eqn.5) yielded the best result. Finally, in Tabriz station equation 7 which uses both temperature and rainfallgained priority in relation to the others. The results of significance test of slope and intercept values (at 5% level of confidence) indicated that in Mashhad station only and for years of 2001 and 2002 (in equations 1,3,6 and 7) the H 1 hypothesis for
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Impact of Implementing a Dedicated Outdoor Air System in Parallel with a Multi-Zone Variable-Air Volume System on Energy Consumption, Thermal Comfort, and Life Cycle Cost

Impact of Implementing a Dedicated Outdoor Air System in Parallel with a Multi-Zone Variable-Air Volume System on Energy Consumption, Thermal Comfort, and Life Cycle Cost

In addition, for a medium office building in 7 climate zones, Frink in [ 17 ] compared the life cycle cost of three alternative configurations utilizing DOAS with multi-zone VAV to a baseline configuration, Alternative 1, utilizing multi-zone VAV. The considered alternative configurations: Alternative 2: a DOAS supplying outdoor air at an optimized temperature in parallel with multi-zone VAV; Alternative 3: a DOAS supplying dehumidified outdoor air at a neutral temperature in parallel with multi-zone VAV; Alternative 4: a DOAS supplying outdoor air at a minimum temperature and a maximum dew point to multi-zone VAV. The results obtained by “whole building energy simulations” showed an increase in energy consumption in all alternatives and climates compared to Alternative 1, except Alternative 2 in Houston, TX; the consumption decreased by 0.4%. Moreover, in terms of life cycle cost, the payback period in the best case, which occurred in Houston, TX, would be 72 years, at least. However, the considered building type, which was an office building, has low ventilation requirements. Such building might not show the benefit of DOAS since the benefit correlates with the ratio of ventilation air to the recirculated air; as the ratio increases, the benefit increases [ 7 ] in [ 6 ]. Hence, considering a building with higher ventilation requirements would show the benefit of DOAS clearly. For instance, according to ASHRAE 62.1-2016, a 100-m 2 space as a
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Effect of Vertical Urban Surfaces on Human Thermal Comfort in Outdoor Environment

Effect of Vertical Urban Surfaces on Human Thermal Comfort in Outdoor Environment

habitable outdoor spaces so that they improve the outdoor activities. User experience of space is greatly affected by the thermal comfort level of that space. Metropolitan cities and city squares are facing challenges of increased heat at microclimatic scale. Cities are facing challenges to mitigate the environmental impact due increased surface area of buildings [2].Due to thermal discomfort people have declined the use of public open spaces. Lots of public spaces became dead spaces during the daytime. Merely because there are not habitable. Which creates cultural gap due to lack of interaction between people in outdoor areas which also affect the neighborhood livability, street life, outdoor activities etc. The professionals such as Architects, landscape architects, urban designers should intervene in these situations to make cities habitable to live. Innovative approaches to urban open spaces will become more important as the Indian population is becoming more urban. Research and solutions are focused mainly on the pollution, greenhouse gases, burning of fossil fuels for urban climate change, whereas the whole surface area of a building contributes to the heat emission in higher quantity. Design of vertical surfaces will show designers how to work to create climatically habitable spaces for human activities. With remarkable clarity, it covers both the scientific background and the design techniques needed for shaping spaces that increase comfort and reduce energy consumption.
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Investigation Of Air Flow In Chamber Using Air-Conditioning Unit For Thermal Comfort

Investigation Of Air Flow In Chamber Using Air-Conditioning Unit For Thermal Comfort

In fact of hostile environment, the design specification for a comfort conditioning system is intended to be the framework for providing a comfortable environment for human being throughout the year. The comfort zones are intended to provide acceptable thermal environment for occupants wearing typical indoor clothing and at a near sedentary activity. To be comfortable, people require a certain amount of ambient humidity that not too high, and not too low.

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Impact of Air Conditioning Systems on the Outdoor Thermal Environment during Summer in Berlin, Germany

Impact of Air Conditioning Systems on the Outdoor Thermal Environment during Summer in Berlin, Germany

with the same building parameters for all grid cells. Various studies have estimated the AC energy consumption and analyzed the increase of the cooling load caused by UHI. [ 20 , 21 ] report the AC consumption for Phoenix of up to 3 W m −2 . This value is less than in our study because the buildings in Phoenix are 1 to 2 floors and are with very low density. The UHI impact on building energy performance has a broad spectrum based on previous studies. Santamouris [ 65 ] derived an average increase of 13% due to UHI in general. Cui et al. [ 66 ] concluded a similar rate of 11% for Beijing. Based on Xu et al. [ 23 ], an increase of 31% and 20% is observed in Beijing for an urban office building and an urban residential building, respectively, from suburban simulations. Concerning residential buildings, the sensible cooling load is increased by UHI intensity by 18% to 28% in Barcelona [ 19 ]. Compared to the rural case, 41% of the cooling load is increased for a non-insulated building in Milan [ 18 ]. All of these values fall in the same order of magnitude and are comparable with the results for Berlin reported here.
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Future context for thermal comfort: Impact of a changing climate on energy demand and human thermal comfort

Future context for thermal comfort: Impact of a changing climate on energy demand and human thermal comfort

Building energy consumption is influenced by many design and operational factors, but weather plays a major role. As discussed in detail in Rabideau, Passe and Takle in “Exploring Alternatives to the ‘Typical Meteorological Year’ for Incorporating Climate Change into Building Design,” “future typical meteorological year” (FTMY) data were constructed for the location Mason City Iowa to evaluate the impact of climate change on buildings. The process used in this project involved several steps. First, the “typicalness” of the TMY3 derived by Wilcox and Marion (2008) was evaluated for seven variables - total sky cover, dry-bulb temperature, dew-point temperature, relative humidity, absolute humidity, pressure, and wind speed. The second step was to evaluate the skill of individual RCMs to reproduce TMY3 data. For the final step, data for Mason City, Iowa were extracted from the NARCCAP archive for the eight GCM/RCM model combinations for both the contemporary (1971-2000) and future (2041-2070) time periods. Differences of the monthly averages of these datasets for each variable were then added to the hourly TMY3 data to produce a future typical meteorological year analogous to the TMY3 for the middle of the 21st century. Linear interpolations between the 3-hourly NARCCAP projected changes were made in order to correspond with the hourly TMY3 data. Results presented here represent low-change (WRFG-CGCM3), medium-change (RCM3- CGCM3), and high-change (CRCM-CCSM) scenarios.
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On the impact of the wind speed on the outdoor human comfort: a sensitivity analysis

On the impact of the wind speed on the outdoor human comfort: a sensitivity analysis

The objective of this paper is to understand how the wind influences thermal energy exchanges, and to quantify its impact on the outdoor thermal sensation. In order to do so, three comfort models, Predicted Mean Vote (PMV), Physiological Equivalent Temperature (PET) and the COMFA* budget were selected. Each thermal model is then calculated by means of the software CitySim and RayMan for the EPFL campus (Switzerland), by coupling the software tools. In order to factor the importance of local meteorological data, two different sources of data are used: (i) the software Meteonorm and (ii) monitoring data from the MoTUS campaign at the EPFL campus. The analyses are performed for the Rolex Learning Center, the library of the campus, as this area is particularly appreciated by visitors and students, and is one of the most liveable places on the campus. The output provided by CitySim and RayMan is then used to create a Comfort Map, where the thermal perception of the pedestrian is designed according to various wind profiles. Results obtained by these analyses underline the impact of the wind speed on the thermal perception of pedestrians, describing the different sensibility of each of the thermal models, as well as the function of the environmental characteristics (ground covering, shadowing, greening and trees). Finally, the impact of a correct meteorological data is also underlined, showing how the provisional thermal sensation could vary depending on whether recorded weather data or yearly averaged data are used.
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Analysis of Outdoor Human Thermal Comfort within Three Major Cities in Egypt

Analysis of Outdoor Human Thermal Comfort within Three Major Cities in Egypt

There are many indices that have been suggested and employed throughout the open literature to assess the outdoor human thermal comfort. Throughout the literature; there are about 40 indices of thermal comfort [1]. Some of these indices, such as the Discomfort Index (DI) [2], Robaa index (RI) [3] [4], and the Predicted Mean Vote index (PMV) [5] [6] merit special mention as they appear continuously in literature. The Discomfort Index was first proposed by Thom in 1959 [2]. It is an empirical index based on a large series of observations and it is only function of air dry bulb temperature and relative humidity. The second index is the Robaa index [3]. It is suggested by Robaa [4] to account for the combined effect of the three weather elements, dry bulb air tempera- ture, relative humidity and wind speed, on the human discomfort. The range of applicability of RI is wide and it was proven to be adequate for Egypt’s climate [4]. It illustrates the integrated effect of both wind speed and rel- ative humidity changes on the human thermal comfort. In this study, both DI and RI are employed for three ma- jor cities in Egypt in order to clarify the effect of the differences in climate at the northern, middle and southern parts of Egypt on outdoor human thermal comfort. The cities are: Alexandria city which is located in the north of Egypt, Cairo the capital of Egypt which is located in the middle and Aswan city which is located in the south of Egypt (See Egypt map in Figure 1). The study investigation is based on the mean hourly measured meteoro- logical data for the three cities, over a period of thirteen months ranging from January 2011 to January 2012.
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Outdoor thermal comfort within five different urban forms in the Netherlands

Outdoor thermal comfort within five different urban forms in the Netherlands

ENVI-met as a CFD program has been previously validated in different climates and countries such as Germany (Freiburg) [69], China (Guangzhou) [70], Singapore (Singapore) [71], Japan (Saga) [72], Morroco (Fez) [54] USA (Phoenix) [73], and UAE (Dubai) [74]. The programmer of ENVI-met states that because the vertical long-wave flux divergence is not taken into account, this could result in a temperature difference of 2 to 4 °C between measurement and simulation [75]. In this research, ENVI-met is also validated for a case in the Netherlands. The maximum deviation of the simulation from the measurements is 2.5°C at 10:00 AM. Moreover, because ENVI-met does not consider cloudiness of sky, simulation of sunny days could be more realistic. In the boundry sensitivity check process, making the reference models when they are standing alone versus in a larger context with neighbouring blocks, showed small differences in air temperature. Therefore, the rest of the simulations in this research are with the mentioned knowledge on reliability about ENVI-met as the research tool.
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A Model-Based Approach to Measuring the Effect of Shading on Outdoor Thermal Comfort

A Model-Based Approach to Measuring the Effect of Shading on Outdoor Thermal Comfort

system as shown in Fig. 1. The symmetric urban system comprises sixteen square blocks, although only the inner 9 blocks are considered for the mobility decisions. Each block measures m × n (m), and is occupied by a single building. The implication of this assumption is that the distance between buildings in each block is negligible. We consider building height and density as the design parameters of urban built form. For simplicity, it is assumed that all buildings have the same height h (m). Since building size is fixed for the case study presented in the next section, the difference in building density is a product of the distances between buildings. It is assumed that the distance between buildings equals the sum of the street and sidewalk width, thus making the entire block made up by a building with no front or dead spaces. Furthermore, we assume that population is evenly distributed in the specified urban system. The above assumptions allow us to examine and compare the impact of geometry alone, foregoing the complexities found in real urban textures. The attractiveness of these generic forms lie mainly in their simple and repeatable characteristics, which allows a more systematic comparative analysis on the effects of different design parameters on mobility patterns [6].
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